The 2010 disaster at the Upper Big Branch mine in West Virginia demonstrated the destructive violence of a coal dust explosion by killing 29 miners in the worst mining accident the United States had experienced in almost 40 years. A major contributing factor to this explosion was that mine operators did not then have a reliable and repeatable way of objectively sampling mine dust before it is analyzed for its combustible/explosive and inert composition.
Coal dust in underground coal mines is potentially explosive. Stone dust is added to the coal dust to render the combined mine dust inert. To demonstrate and document inertization, mine dust must be sampled regularly. Samples are analyzed on-site and in the laboratory to confirm that they comprise at least 80% inert components, as required by 30 C.F.R. § 75.403, to prevent devastating coal dust explosions. Currently, mine dust samples are taken with a pan and brush to an estimated depth of ⅛ inch, following sampling guidelines by the U.S. Mine Safety and Health Administration (MSHA). This method of sampling is subjective and does not take into account that an explosion scours up mine dust through pneumatic entrainment. Therefore, samples collected mechanically with a pan and brush may not correctly reflect the portion of mine dust that would be scoured up during an explosion. Additionally, samples collected using the pan-and-brush method are subject to human error (resulting, for example, from failure to collect all brushed dust in the pan, and/or failure to brush to a depth of ⅛ inch) and inconsistent results (due, for example, to the difficulty of applying the same brushing force during every sample collection, and to the difficulty of brushing to a depth of exactly ⅛ inch). Still further, the pan-and-brush method of collecting dust samples is time consuming, requiring careful brushing of a dusty surface to ensure that the proper amount of dust is collected. Suitable instruments for, and an accurate, consistent method of, collecting rock dust samples to test for explosibility do not currently exist.